Wire saw and process for slicing multiple semiconductor ingots

ABSTRACT

A wire saw ( 10 ) for simultaneously slicing multiple, generally cylindrical monocrystalline ingots ( 14 ) into wafers. The wire saw includes a cutting head ( 16 ), an ingot support ( 12 ), and multiple generally parallel lengths of cutting wire ( 18 ) defining a cutting web ( 30 ). A slurry delivery system includes nozzles ( 34, 36 , and  38 ) positioned for dispensing slurry along the wire web generally at lateral sides of each ingot. A process for simultaneously slicing at least two generally cylindrical semiconductor ingots into wafers includes mounting at least two ingots to a common ingot support, moving the ingot support relative to the cutting web so that the two ingots simultaneously press against the cutting web at cutting regions, and dispensing a liquid slurry to at least three locations on the wire web including two outermost sides of the cutting regions and a location between each pair of ingots.

BACKGROUND OF THE INVENTION

This invention relates generally to cutting monocrystallinesemiconductor ingots into multiple wafers, and in particular to anapparatus and method for simultaneously slicing at least twosemiconductor ingots to improve throughput.

Semiconductor wafers are generally prepared from a single crystal ingot,such as a silicon ingot, that is cylindrical in shape. The ingot issliced in a direction normal to its longitudinal axis to produce as manyas several hundred thin, disk-shaped wafers. The slicing operation maybe accomplished by means of a wire saw, wherein the ingot is contactedwith a reciprocating wire while a liquid slurry containing abrasivegrains is supplied to a contact area between the ingot and the wire. Asthe abrasive particles in the slurry are rubbed by the wire against theingot, silicon crystal is removed and the ingot is gradually sliced. Thewire saw provides a gentle mechanical method for slicing which makes itideal for cutting silicon crystal, which is brittle and could be damagedby other types of saws (e.g., conventional internal diameter saws).After slicing, each wafer is subjected to a number of processingoperations to reduce the thickness, remove damage caused by the slicingoperation, and create a flat and highly reflective surface suitable forinstallation of integrated circuit devices.

Wire saws generally have three or four rollers which are rotatablymounted on a frame, each roller having guide grooves for receivingsegments of wire. Multiple parallel lengths of the wire extend betweentwo of the rollers to form a wire web for slicing the ingot intomultiple wafers. The space between adjacent wires in the web generallycorresponds to the thickness of one wafer before processing. Theapparatus includes an ingot support that may mount one silicon ingot andis adjustable to accurately align an orientation of the crystallinestructure of the ingot relative to a cutting plane. The support ismoveable in translation to bring the ingot into contact with the wireweb.

Slurry is transported from a nearby slurry container to the wire by apump, tubing, and at least one nozzle which dispenses slurry onto thewire web. A portion of the slurry then moves with the wire into acontact area between the wire and the ingot where the silicon crystal iscut. Typically, there are two nozzles positioned on opposite sides ofthe ingot holder so that slurry is dispensed onto the web on both sidesof the ingot, thus facilitating delivery of slurry to the cutting regionfor either direction of travel of the reciprocal wire. Each nozzle ispositioned above the wire web at close spacing and configured todispense slurry in a generally thin, linear distribution pattern,forming a curtain or sheet of slurry. The slurry curtain extends acrossa full width of the wire web so that slurry is delivered to every reachof wire and every slice in the ingot.

A substantial concern when slicing semiconductor ingots is maintainingflatness of the wafers that are cut by the wire saw. One key to avoidingthickness variation and warp on wafer surfaces is controlling build upof frictional heat at the contact area, or cutting region. Accordingly,the liquid slurry is actively cooled prior to dispensing on the wire webso that it may remove heat as it passes through the cutting region. Aheat exchanger is typically located between the container and the nozzlefor cooling the slurry.

A limitation to the process of slicing semiconductor ingots is that itrequires a substantial amount of time and can become a hindrance to theefficient production of wafers. It is desirable to slice the ingots asquickly as possible to improve throughput and reduce costs, yet therehave been difficulties implementing a more rapid wire sawing process.The speed of the cutting wire cannot be substantially increased becausethat would elevate temperature at the cutting region to the detriment ofthe flatness of the wafers.

Thus, there is presently a need for improving the throughput of wiresaws without compromising quality of the wafers cut.

SUMMARY OF THE INVENTION

Among the several objects and features of the present invention may benoted the provision of an apparatus and process to improve throughput inslicing semiconductor ingots into wafers; the provision of such anapparatus and process that simultaneously slice multiple ingots; theprovision of such an apparatus and process to produce flat, high qualitywafer slices; the provision of such an apparatus and process that slicemultiple ingots having different lengths; and the provision of such anapparatus and process that is economical.

In general, a wire saw of the present invention simultaneously slicesmultiple, generally cylindrical monocrystalline ingots into wafers. Thewire saw comprises a frame including a cutting head and an ingotsupport. The cutting head comprises a cutting wire adapted to cutthrough the ingots and wire guide rollers mounted on the frame andsupporting the wire for lengthwise movement of the wire. The wire issupported by the rollers in reaches between adjacent rollers. Each reachincludes multiple generally parallel lengths of the wire for cuttingmultiple wafers from the ingots, at least one of the reaches defining acutting web. The ingot support is adapted for mounting at least twoingots thereon in registration with the cutting web and withlongitudinal axes of the ingots generally perpendicular to thelengthwise extent of the wire in the cutting web. The frame mounts thecutting head and ingot support for relative motion such that the ingotsmounted on the ingot support pass through the cutting web as the wire isdriven in a lengthwise direction for substantially simultaneous slicingof wafers from the ingots by the wire.

In another aspect, a process of the present invention simultaneouslyslices at least two generally cylindrical semiconductor ingots intowafers using a wire saw having a moveable cutting wire arranged ingenerally parallel reaches between guide rollers. At least one of thereaches defines a cutting web, the wire being adapted to cut through theingots. The process comprises the steps of mounting at least two ingotsto a common ingot support so that the ingots are positioned inregistration with the cutting web and with longitudinal axes of theingots generally perpendicular to the lengthwise extent of the wire inthe cutting web. The ingot support is moved relative to the cutting webso that the at least two ingots simultaneously press against the cuttingweb at cutting regions where the ingots engage the wire web. A liquidslurry is dispensed to at least three locations on the wire web, thelocations including two outermost sides of the ingot cutting regions anda location between each pair of ingots.

Other objects and features of the present invention will be in partapparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a wire saw of the presentinvention having two semiconductor ingots mounted thereon;

FIG. 2 is a schematic perspective view of the wire saw having threeingots mounted thereon;

FIG. 3 is a schematic perspective view of the wire saw having a stackedarrangement with four ingots mounted thereon;

FIG. 4 is a schematic perspective view of the wire saw having a stackedarrangement with six ingots mounted thereon;

FIG. 5 is an enlarged, schematic sectional view of a structure forattaching ingots to an ingot support;

FIG. 6 is a schematic elevational view of a second embodiment of thepresent invention having a double adaptor for holding two ingots;

FIG. 7 is a schematic elevational view of the second embodiment with atriple adaptor for holding three ingots;

FIG. 8 is a schematic perspective view of a third embodiment of thepresent invention having a central support with a single verticalmember;

FIG. 9 is a schematic perspective view of the third embodiment having acentral support with two vertical members;

FIG. 10 is a schematic plan view of a cutting wire web in relation totwo ingots of different lengths;

FIG. 11 is a schematic plan view of a first example of a pairedcombination of ingots that does not have need for a central support;

FIG. 12 is a schematic plan view of a second example of a pairedcombination of ingots that does not have need for a central support;

FIG. 13 is a schematic plan view of a third example of a pairedcombination of ingots that does not have need for a central support; and

FIG. 14 is a schematic plan view of a fourth example of a pairedcombination of ingots that does not have need for a central support.

Corresponding reference characters indicate corresponding partsthroughout the views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings and in particular to FIG. 1, a wire saw ofthe present invention for simultaneously slicing a plurality ofsemiconductor ingots into wafers is indicated generally at 10. The wiresaw 10 has an ingot support generally indicated at 12 for holding ingots14. A cutting head indicated generally at 16 mounts a wire 18 forreciprocal movement to cut ingots. The ingot support 12 is configuredfor holding conventional monocrystalline silicon ingots 14, which aregenerally cylindrical in shape, in a generally side-by-side arrangementwith longitudinal axes of the ingots being non-collinear andapproximately parallel. Ingots 14 are sliced when they are engagedagainst the moving cutting wire 18 in the presence of an abrasive liquidslurry. The ingot support 12 and cutting head 16 are moveable relativeto each other so that the ingots 14 may be moved into or out ofengagement with the cutting wire 18, and other relative movementsbetween the cutting head and ingot support to facilitate cuffing as areknown to those of ordinary skill in the art.

The cutting head 16 includes rotatable wire guiding rollers 22 aroundwhich the cutting wire 18 is looped for circuitous motion around therollers. Preferably, there are four guiding rollers 22 in a generallyrectangular arrangement, although saws having fewer or greater number ofrollers and at other arrangements do not depart from the scope of thisinvention. The ingot support 12 is positioned generally above therectangular arrangement of the rollers 22, so that the ingots 14 areengageable against only a topmost section of cutting wire 18 extendingbetween the two uppermost rollers. However, the ingot support 12 couldbe positioned anywhere about the rollers 22 so that the ingots 14 mayengage any section of wire 18. Preferably, the ingot support 12 andcutting head 16 are mounted on a common support frame 24, with thecutting head being fixed relative to the frame while the ingot supportis moveable relative to the frame. As slicing is accomplished the ingots14 gradually move through the cutting wire 18 as the wire penetrates theingots. The ingot support 12 continues moving generally toward thecuffing head 16 to keep the ingots 14 engaged against the wire 18 at acontact area within each slice.

The cutting wire 18 is supported by the rollers in multiple generallyparallel reaches between the rollers 22 for cutting multiple wafers fromthe ingots 14. Each of the reaches includes multiple generally parallellengths of wire 18, each length cutting one slice in each ingot.Collectively the parallel reaches of the wire 18 on the guide rollers 22define a cutting web, indicated generally at 30. The wire web 30 mayhave as many as several hundred parallel lengths of wire 18 for cuttinga corresponding number of slices, although a web formed of any number oflengths does not depart from the scope of this invention. At least oneof the rollers 22 is connected to a motor or other suitable drivemechanism (not shown) for providing power to drive the wire 18 in alengthwise direction for operation of the wire saw 10. Each roller 22has a plurality of annular grooves (not shown) around its circumferenceadapted for receiving the lengths of the cutting wire 18. The wirereciprocates in lengthwise motion as driven by the rollers 22. As knownto those skilled in the art, the wire 18 moves in a forward directionfor a first predetermined time or length displacement, and then moves ina reverse direction for a second predetermined time or lengthdisplacement. The wire 18 may extend in a conventional manner into atake up reel and a discharge reel (not shown) for collecting excesslength of the wire that is not presently looped around the guide rollers22.

The wire saw 10 has a slurry system for supplying an abrasive liquidslurry to a portion of the wire web 30 for delivery along the wire 18 tocontact regions between the wire and the ingots 14. In the preferredembodiment, three nozzles 34, 36, 38 are positioned for dispensing theslurry onto the wire. Each nozzle is configured in a conventionalmanner, as known to those skilled in the art, generally as a slit thatdispenses slurry downwardly in a thin, planar distribution patternforming a curtain or sheet 40. The curtain 40 of slurry is orientedperpendicular to the wire 18 and has a length that is approximately thesame as a width of the wire web 30. Each nozzle 34, 36, 38 receivesslurry from a suitable slurry container, a pump, and a length of tubing(not shown), each of these elements being conventional in nature andoperable to transport slurry from the container to the nozzles. Thesystem can include a manifold directly adjacent each nozzle for holdinga small quantity of slurry. During operation, a total flow of slurry maybe actively distributed at any different proportions among the nozzles34, 36, 38, or may be passively distributed in equal portionstherebetween.

To control heat, the liquid slurry is actively cooled prior todispensing on the wire web 30. As known to those skilled in the art, aheat exchanger (not shown) is located either between the slurrycontainer and each nozzle or at the container. In practice, it has beenfound useful when slicing two or more ingots 14 at the same cuttingspeed as with one ingot to cool the slurry to a temperature of 25° C.,whereas 30° C. slurry is typically provided for slicing a single ingot.This is accomplished in the present invention by the inclusion of asecond heat exchanger in the container. However, a single larger heatexchanger or other cooling mechanisms and temperatures do not departfrom the scope of this invention.

The nozzles 34, 36, 38 are positioned so that slurry is carried by thewire 18 into the contact area between the wire and each ingot 14 foreither direction of travel of the wire. As shown in FIG. 1, first andsecond nozzles 34, 36 are positioned generally above the wire web 30 onopposite sides of the ingot support 12 so that slurry is dispensed ontothe wire web on both sides of the ingot support. The first and secondnozzles 34, 36 are preferably mounted to the support frame at a fixedposition relative to the cutting head 16, and they do not move alongwith the ingot support 12 as it moves relative to the cutting head. Thefirst and second nozzles 34, 36 are located at a suitable close spacing(such as 2 cm) above the wire web 30 so that slurry falls upon everylength of wire 18, including particularly the lengths on each endextremity of the width of the web 30. The slurry is preferably collectedand recycled in a conventional manner.

The present invention further includes the third nozzle 38 (FIG. 1)positioned generally above the wire web 30 and mounted on the ingotsupport 12. Although wire saws of the prior art for slicing a singleingot have included first and second nozzles 34, 36, the third nozzle 38is included in the present invention to provide delivery of adequatequantity and distribution of slurry to two ingots 14. Each ingotreceives slurry on both lateral sides of the ingot. Because the thirdnozzle 38 is attached to the ingot support 12, the third nozzle movesalong with the ingot support as it moves relative to the cuffing head16. Nozzles having other locations and mounts do not depart from thescope of this invention.

Two bars 46 extend vertically downward from opposite ends of the thirdnozzle 38 to inhibit bunching of the slurry and facilitate good slurrydistribution. Only one of the bars 46 is visible in FIG. 1. Unlike thefirst and second nozzles 34, 36, which are fixed at a closely-spacedposition above the wire web 30, the third nozzle 38 moves with the ingotsupport 12 to a substantial distance from the wire (such as 30 cm). Thethin curtain of slurry 40 dispensed from the third nozzle thus falls afarther distance before reaching the wire. In practice, an unboundedcurtain of slurry naturally tends to coalesce in shape as it descends,bunching toward a narrower profile. The slurry dispensed from the nozzle38 may fall a distance sufficient for the original linear pattern todegrade so that slurry does not fall upon lengths of wire near each endextremity of the web 30.

The bars 46 correct this problem by providing a surface against which anedge of the curtain 40 of slurry adheres due to surface tension effectsor other fluid dynamics. In practice, inclusion of the bars 46 hasinhibited the tendency of the slurry to coalesce and has resulted insubstantially maintaining the original width of the slurry until itreaches the wire web 30. Thus, the slurry is distributed to every lengthof wire 18, including particularly the lengths on each end extremity ofthe width of the web, so that slurry is delivered to every slice in theingot. The bars 46 are generally thin in construction and positioned toextend from each end of the third nozzle 38. The bars 46 do notinterfere with motion of the wire web 30 when the ingot support 12 ismoved toward the web. The bars 46 may have a variety of section shapes,diameters, and lengths. Preferably, the length is about equal to amaximum operating distance between the third nozzle 38 and the wire web30.

The wire saw 10 may hold two or three ingots 14 in a side-by-side,horizontal arrangement, as shown in FIGS. 1 and 2, respectively, or mayhold a single ingot as in a conventional wire saw. Although the ingotsupport 12 may be used with differently sized ingots, in practice in hasbeen useful for holding two 150 mm diameter ingots (FIG. 1), three 100mm diameter ingots (FIG. 2), or a single 300 mm diameter ingot. Thenozzles for dispensing slurry are numbered in an amount of at least onemore than the number of side-by-side ingots 14. For example, with twoingots 14, there are three nozzles 34, 36, 38. With three ingots 14,there are four nozzles. The ingots and the nozzles are arranged inalternating relative positions so that slurry is dispenses at distinctlocations generally at lateral sides of every ingot is 14.

The ingot support 12 may hold up to four or six ingots, as shown inFIGS. 3 and 4, respectively, when pairs of ingots are stacked generallyvertically. Stacking reduces down-time of the wire saw because itincreases the number of ingots 14 sliced before it is necessary to stopoperation to load new ingots or change 20 configurations, thus providingimproved efficiency. After lower ingots are sliced, operation maycontinue to slice upper ingots. It is understood, however, that otherarrangements, including any number of ingots and non-horizontal andnon-vertical relative ingot positions, do not depart from the scope ofthis invention.

Referring now to FIG. 5, a preferred structure for attaching ingots 14to the ingot support 12 is indicated generally at 50. Each ingot isattached by a conventional epoxy to a mounting beam 52 having a concavesurface 54 corresponding to the convex, cylindrical outer surface of theingot 14. As known to those skilled in the art, the crystallographicplane of the silicon crystal lattice is carefully oriented relative tothe mounting beam 52 using x-rays or other suitable technique to a closeangular tolerance such as within one-fourth of one degree. The mountingbeam 52 is adapted for connection to a plate 56 that is in turnconnectable to a dove tail support 58.

The ingot support 12 has a receptacle along its lower side in the formof a slot 60. An internal shoulder 62 with a sloped surface is locatedwithin the slot. The dove tail support 58 is receivable in the slot 60,wherein a first sloped surface 66 on the support 58 slidably engages thesloped surface on the shoulder 62. A clamp, indicated generally at 68,is provided for locking the support 58 at a fixed position in the slot.The clamp includes an engaging block 70 having a sloped surface that isengageable against a second sloped surface 72 on the support 58. A shaft74 connects the block 70 to a mechanical or hydraulic actuator (notshown). The block 70 and shaft 74 are moveable between an unlockposition where the block does not press against the dove tail support 58and the support can be moved lengthwise in the slot 60, and a lockedposition where the block presses against the dove tail support and thesupport is at a fixed position in the slot. Other structures forattaching ingots to the ingot support do not depart from the scope ofthis invention.

For the stacked configurations of FIGS. 3 and 4, pairs of ingots arejoined by epoxy to an intermediate mounting beam 76 that is sandwichedbetween the ingots 14. Each of these mounting beams 76 hasconcavely-shaped upper and lower surfaces, corresponding to the convexshape of the cylindrical outer surface of each ingot 14. The stackedpairs of ingots are carefully oriented so that their respectivecrystallographic planes are aligned.

A second embodiment of the invention is shown schematically andindicated generally at 80 in FIGS. 6 and 7. The second embodiment 80includes adaptors 82, 84 for readily converting the wire saw betweenconfigurations for slicing one, two, or three side-by-side ingots 14.The ingot support 12 has a common loading platform or head 86 with areceptacle along its lower side in the form of a slot 88. Although theslot 88 may have a variety of shapes or structure for attaching ingots,preferably the slot is configured as discussed above for the slotreceptacle 60 on the ingot support 12 of the first embodiment, and asshown in FIG. 5. A double adaptor 82 (FIG. 6) is configured for holdingtwo ingots 14, although it can also hold only one ingot, or in a stackedconfiguration, three or four ingots. The double adaptor 82 has amounting ridge 90 on its upper surface that is engageable in the slot 88of the head 86. Preferably, the ridge 90 is shaped as a dove tailsupport 58 as in FIG. 5. A triple adaptor 84 (FIG. 7) is configured forholding three ingots 14, although it can also hold one or two ingots, orin a stacked configuration, from four to six ingots. The triple adaptor84 also has a mounting ridge 90 of the same size as that on the doubleadaptor 82. The invention provides flexibility in that the slot 88 isconfigured to receive and lock therein either: a) support 58 formounting a single ingot 14 for sawing a single ingot, b) the ridge 90 ofthe double adaptor 82 for sawing two ingots, or c) the ridge 90 of thetriple adaptor 84 for sawing three ingots. There may be other adaptors,including those with different structure or for holding four or moreside-by-side ingots, without departing from the scope of this invention.

A third embodiment of the invention is shown schematically and indicatedgenerally at 100 in FIGS. 8 and 9. The third embodiment 100 has acentral support (designated generally at 102) configured to limitdeflection of the wire web 30 when it is engaged by one or more ingots14. The central support 120 comprises at least one obstruction to freevertical deflection of wire, and it is preferably fixed relative to therollers 22 of the cutting head 16. The central support 102 is locatedgenerally within an interior of a rectangular shape defined by the wireweb 30 and adjacent the wire web on an opposite side of the wire webfrom the ingots 14. The central support 102 has a generally verticalmember 104 that is attached to a platform 106. The platform 106 ispreferably mounted to the common support frame 24.

The central support 102 has a suitable upper end 103 for permitting wire18 to engage and move therepast, such as a plurality of rollers, and itextends across the full width of the wire web 30. For the double adaptor82, a single vertical member 104 is provided (FIG. 8), and for thetriple adaptor 84, two vertical members 104 are provided (FIG. 9). Eachcentral support 102 is located so that it is about equally spacedbetween two ingots 14. When the ingot support 12 moves downwardly andone or more ingots engage the wire web 30, the web is deflected until itengages the central support. The wire 18 will not deflect further at thelocation where it engages the central support 102. The central supportmay have a different construction, particularly including obstructionsof other shapes or with no vertical members 104, without departing fromthe scope of this invention.

A problem when there is no central support 102, as in the firstembodiment, is that the yield of wafers is detrimentally reduced whentwo (or three) ingots that are simultaneously sliced have differentlengths. If there are two ingots in side-by-side arrangement and thelengths of these ingots are not substantially equal, then at least somelengths of the wire 18 will engage one ingot while other lengths of wireengage two ingots. As shown schematically in FIG. 10, the length of wirenumbered 110 is engaged by one ingot while the length of wire numbered112 is engaged by two ingots. The space between adjacent lengths of wireis exaggerated in FIG. 10 for clarity. The lengths 110 and 112 will havedifferent deflection patterns and different tension force in the wire.Wafers that are sliced from the longer ingot by reaches of wire that arein a transition region where the wire tension changes do not receiveeven slicing, resulting in warp or poor wafer quality. As a result,operators are forced to slice only ingots with substantially equallengths, or in multiple ingot pairs having substantially equal lengths,as shown in FIG. 11.

The combinations of ingot lengths shown in FIGS. 11 through 14 do notdegrade yield, while the combination of FIG. 10 does result in degradedyield. The combination of FIG. 10 has a longer ingot that extendscontinuously past a position where a shorter ingot ends and no otheringot is located. In contrast the combinations of FIGS. 11 through 14nowhere have a longer ingot that extends through a transition regionnear the end of a shorter ingot. Therefore there are no wafers slicedfrom a longer ingot that are affected by different wire tensions. OnFIG. 14, a combination of two ingots 14 having different length must besliced with the addition of a scrap rod 114. The scrap rod 114 must havethe same external diameter as the ingots 14 being sliced, and mustextend at least to the full length of the longer ingot. The scrap rod114 does not need to be silicon, but can be a different material. Thescrap rod provides a uniform wire deflection across an entire length ofthe longer ingot.

The central support 102 prevents this problem by precluding theinfluence of ingot length on the wire tensions. Because the centralsupport 102 extends across the entire width of the wire web 30, allreaches engage the central support. That results in locally uniformdeflections and tensions to maintain even slicing, low warp, and highyield. The central support permits operators to simultaneously sliceingots of varying lengths, such as in FIG. 10.

In operation, the wire saw 10 of the present invention simultaneouslyslices at least two generally cylindrical semiconductor ingots 14 intowafers. First, each ingot is attached to a mounting beam 52 by asuitable epoxy. This can be accomplished in a conventional manner with aseparate device that uses x-rays for carefully aligning thecrystallographic plane of the ingot relative to the mounting beam withina close tolerance. The mounting beams are each attached to dove tailsupports 58 and secured to the ingot support 12 by inserting the dovetail in slots 60 and locking the clamps. The ingots 14 are automaticallypositioned to be in registration with the cutting web 30 and withlongitudinal axes of the ingots generally perpendicular to thelengthwise extent of the wire. If an adaptor 82 or 84 of the secondembodiment 80 is used, two or three mounting beams are secured to theadaptor, and then the adaptor is attached to the head 86 by securing theridge 90 in the slot 88. The ingot support 12 is moved relative to thecutting web so that the ingots simultaneously press against the cuffingweb at cuffing regions where the ingots engage the wire. The liquidslurry is dispensed from nozzles 34, 36, 38 to the wire web at locationsincluding two lateral sides of each ingot. When a stacked arrangement isused, additional ingots and mounting beams are aligned and attached tothe first mounting beams, generally before attaching to the ingotsupport.

The apparatus may be readily configured for slicing a single 300 mmdiameter ingot, from one to four 150 mm diameter ingots, or from one tosix 100 mm diameter ingots. For slicing two ingots in side-by-sidearrangement, it has been found that productivity is double that ofprevious wire saws, while wafer flatness and quality are maintained atthe same level.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results obtained.

When introducing elements of the present invention or the preferredembodiment(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

As various changes could be made in the above without departing from thescope of the invention, it is intended that all matter contained in theabove description and shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

1. A process for simultaneously slicing at least two generallycylindrical semiconductor ingots into wafers using a wire saw having amoveable cutting wire arranged in generally parallel reaches betweenguide rollers, at least one of the reaches defining a cutting web, thewire being adapted to cut through the ingots, the process comprising thesteps of: mounting said at least two ingots to a common ingot support sothat the ingots are positioned in registration with the cutting web andwith longitudinal axes of the ingots being generally parallel,non-coaxial, and generally perpendicular to the lengthwise extent of thewire in the cutting web, said ingot support including at least twomounting beams, each adapted for connection of a respective ingotthereto, a loading platform and an adaptor for holding said mountingbeams, the platform having one receptacle configured to receive saidadaptor and configured to receive one of the mounting beams free fromsaid adaptor for mounting a single ingot for sawing; moving the ingotsupport relative to the cutting web so that said at least two ingotssimultaneously press against the cutting web at cutting regions wheresaid ingots engage said wire web; dispensing a liquid slurry to at leastthree locations on said wire web, said locations including two outermostsides of said ingot cutting regions and a location between each pair ofingots; and removing said adaptor from said receptacle of the ingotsupport and installing either a second adaptor or one mounting beam freefrom said adaptor into said receptacle for slicing at least oneadditional ingot.
 2. A process as set forth in claim 1 furthercomprising cooling said slurry to a uniform temperature of about 25° C.or less prior to dispensing.
 3. A process as set forth in claim 1further comprising a step of mounting at least two ingots in a stackedarrangement wherein said at least two ingots are generally parallel witha first ingot positioned closer to the cutting web than a second,stacked ingot.
 4. A process as set forth in claim 1 wherein said atleast two ingots have different lengths, and further comprising a stepof mounting a scrap rod to the ingot support, the scrap rod beingaligned with a shorter of the ingots and having a length so that acombined length of the shorter ingot and the scrap rod is at least aslong as a longer of the ingots.
 5. A process as set forth in claim 1further comprising obstructing movement of the cutting web caused bysaid step of moving the ingot support to press the ingots against thecutting web for limiting deflection of the web.
 6. A wire saw forslicing generally cylindrical monocrystalline ingots into wafers, thewire saw comprising: a frame including a cutting head and an ingotsupport; the cutting head comprising a cutting wire adapted to cutthrough the ingots, wire guide rollers mounted on the frame andsupporting the wire for lengthwise movement of the wire, the wire beingsupported by the rollers in reaches between adjacent rollers, each reachincluding multiple generally parallel lengths of the wire for cuttingmultiple wafers from the ingots, at least one of the reaches defining acutting web; the ingot support being adapted for mounting at least oneingot thereon in registration with the cutting web and with longitudinalaxes of said one ingot being generally perpendicular to the lengthwiseextent of the wire in the cutting web, the ingot support including:mounting beams, each adapted for connection of a respective ingotthereto, an adaptor for holding said mounting beams, the adaptor beingconfigured for holding multiple mounting beams for mounting multipleingots on the ingot support, and a loading platform having a receptacleconfigured to selectively receive either one of the mounting beams formounting a single ingot for sawing or to receive said adaptor, said onereceptacle thereby providing capability for converting the wire sawbetween configurations for slicing one ingot free from said adaptor andfor slicing multiple ingots with said adaptor; the frame mounting thecutting head and ingot support for relative motion such that the ingotsmounted on the ingot support pass through the cutting web as the wire isdriven in a lengthwise direction for substantially simultaneous slicingof wafers from the ingots by the wire.
 7. A wire saw as set forth inclaim 6 in combination with four ingots, wherein the adaptor is a doubleadaptor configured to hold two mounting beams in side-by-sidearrangement, a first of said ingots being attached to a first of themounting beams mounted on the adaptor, a second of said ingots beingattached to a second of the mounting beams mounted on the adaptor, athird of said ingots being connected to a third mounting beam mounted onsaid first ingot and a fourth of said ingots being attached to a fourthmounting beam mounted on said second ingot.
 8. A wire saw as set forthin claim 6 in combination with six ingots, wherein the adaptor is atriple adaptor configured to hold three mounting beams in side-by-sidearrangement, a first of said ingots being attached to a first of themounting beams mounted on the adaptor, a second of said ingots beingattached to a second of the mounting beams mounted on the adaptor, athird of said ingots being attached to a third of the mounting beamsmounted on the adaptor, a fourth of said ingots being attached to afourth of the mounting beams mounted on said first ingot, a fifth ofsaid ingots being connected to a fifth of the mounting beams mounted onsaid second ingot, and a sixth of said ingots being attached to a sixthof the mounting beams mounted on said third ingot.
 9. A wire saw as setforth in claim 6 further comprising a slurry delivery system includingnozzles, each nozzle being positioned for dispensing slurry at distinctlocations along the wire web generally at lateral sides of each of themounting beams.
 10. A wire saw as set forth in claim 9 furthercomprising two bars extending away from at least one of said nozzles,each bar extending from a location generally at an end of said at leastone nozzle, the bars defining edges of a curtain of dispensed slurry.11. A wire saw as set forth in claim 6 further comprising a centralsupport configured for engagement by said cutting web to limitdeflection of said cutting web when engaging ingots.
 12. A wire saw asset forth in claim 6 wherein the ingot support mounts at least twoingots with longitudinal axes of the ingots being parallel andnon-coaxial.